A New Method for Elastic-Plastic Contact Analysis of a Deformable Sphere and a Rigid Flat

2005 ◽  
Vol 128 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Li Po Lin ◽  
Jen Fin Lin
Keyword(s):  
New Method ◽  
Contact Load ◽  
Rigid Sphere ◽  
The Finite Element Method ◽  
Numerical Errors ◽  
Elastic Regime ◽  
Contact Loads ◽  
Indentation Tests ◽  
Metal Materials ◽  
Contact Parameters

A new method is developed in the present study to determine the elastoplastic regime of a spherical asperity in terms of the interference of two contact surfaces. This method provides an efficient way to solve the problem of discontinuities often present in the reported solutions for the contact load and area or the gradients of these parameters obtained at either the inception or the end of the elastoplastic regime. The well-established solutions for the elastic regime and experimental data of metal materials using indentation tests are provided as the references to determine the errors of these contact parameters due to the use of the finite-element method. These numerical errors provide the basis to adjust the contact area and contact load of a rigid sphere in contact with a flat such that the dimensionless mean contact pressure Pave∕Y (Y: the yielding strength) and the dimensionless contact load Fpc∕Fec (Fec, Fpc: the contact loads corresponding to the inceptions of the elastoplastic and fully plastic regimes, respectively) reaches the criteria arising at the inception of the fully plastic regime, which are available from the reports of the indentation tests for metal materials. These two criteria are however not suitable for the present case of a rigid flat in contact with a deformable sphere. In the case of a rigid flat in contact with a deformable sphere, the proportions in the adjustments of these contact parameters are given individually the same as those arising in the indentation case. The elastoplastic regime for each of these two contact mechanisms can thus be determined independently. By assuming that the proportion of adjustment in the elastoplastic regime is a linear function, the discontinuities appearing in these contact parameters are absent from the two ends of the elastoplastic regime in the present study. These results are presented and compared with the published results.

Semi-inverse method for predicting stress–strain relationship from cone indentations

2003 ◽  
Vol 18 (9) ◽  
pp. 2068-2078 ◽  
Author(s):  
A. DiCarlo ◽  
H. T. Y. Yang ◽  
S. Chandrasekar
Keyword(s):  
A Priori ◽  
Model Material ◽  
Material Behavior ◽  
The Finite Element Method ◽  
Stress Strain ◽  
Indentation Tests ◽  
Strain Relationship ◽  
Initial Force ◽  
Relationship Of ◽  
Force Displacement

A method for determining the stress–strain relationship of a material from hardness values H obtained from cone indentation tests with various apical angles is presented. The materials studied were assumed to exhibit power-law hardening. As a result, the properties of importance are the Young's modulus E, yield strength Y, and the work-hardening exponent n. Previous work [W.C. Oliver and G.M. Pharr, J. Mater. Res. 7, 1564 (1992)] showed that E can be determined from initial force–displacement data collected while unloading the indenter from the material. Consequently, the properties that need to be determined are Y and n. Dimensional analysis was used to generalize H/E so that it was a function of Y/E and n [Y-T. Cheng and C-M. Cheng, J. Appl. Phys. 84, 1284 (1999); Philos. Mag. Lett. 77, 39 (1998)]. A parametric study of Y/E and n was conducted using the finite element method to model material behavior. Regression analysis was used to correlate the H/E findings from the simulations to Y/E and n. With the a priori knowledge of E, this correlation was used to estimate Y and n.

scholarly journals Analysis of depth-sensing indentation tests with a Knoop indenter

2001 ◽  
Vol 16 (6) ◽  
pp. 1660-1667 ◽  
Author(s):  
L. Riester ◽  
T. J. Bell ◽  
A. C. Fischer-Cripps
Keyword(s):  
Elastic Modulus ◽  
Elastic Recovery ◽  
Indentation Test ◽  
New Method ◽  
Short Axis ◽  
Depth Sensing ◽  
Specimen Material ◽  
Indentation Tests ◽  
Conventional Methods ◽  
Knoop Indenter

The present work shows how data obtained in a depth-sensing indentation test using a Knoop indenter may be analyzed to provide elastic modulus and hardness of the specimen material. The method takes into account the elastic recovery along the direction of the short axis of the residual impression as the indenter is removed. If elastic recovery is not accounted for, the elastic modulus and hardness are overestimated by an amount that depends on the ratio of E/H of the specimen material. The new method of analysis expresses the elastic recovery of the short diagonal of the residual impression into an equivalent face angle for one side of the Knoop indenter. Conventional methods of analysis using this corrected angle provide results for modulus and hardness that are consistent with those obtained with other types of indenters.

scholarly journals Design optimization of the satellite in precessional transmission

2018 ◽  
Vol 178 ◽  
pp. 05008
Author(s):  
Stanislav Lealin
Keyword(s):  
Noise Reduction ◽  
Load Capacity ◽  
Elastic Compliance ◽  
Complex Structures ◽  
The Finite Element Method ◽  
Linear Deformation ◽  
Satellite Design ◽  
Deformation Simulation ◽  
Contact Loads ◽  
Radial Channel

One of the important tasks in the design of gears and gearboxes based on them is to increase the load capacity, durability and noise reduction with moderate requirements for manufacturing precision by providing elastic compliance of the teeth with simple satellite manufacturing technology. In the paper is firstly presented a base satellite in a precessional transmission. The design is rigid and non-technological. There was simulated the workload and the results are presented as a linear deformation. Simulation was based on the special module for the calculation and analysis of complex structures using the integrated module Stress Analysis (program Autodesk Inventor Professional 2012). It uses the finite element method calculation, based on the ANSYS program. Then is shown an optimized satellite structure. This option provides an increased durability and noise reduction due to local and general tooth compliance. The main drawback of this satellite is the high laboriousness of making cut-outs in the satellite. In this satellite, by increasing the diameter of the radial channel, it is possible to reduce the wall thickness and thereby increase the compliance. The simulation results of a new satellite design are presented. Compliance increased roughly by 4 times compared to the base version. When the gear is in mesh with the satellite, due to the increased elastic compliance of the teeth, a multi-pairing mesh is achieved, which reduces the contact loads and noise, increases the service life of the transmission.

High Cycle Fatigue Damage Evaluation of Steel Pipelines Based on Microhardness Changes During Cyclic Loads: Part II

2018 ◽  
Author(s):  
Geovana Drumond ◽  
Bianca Pinheiro ◽  
Ilson Pasqualino ◽  
Francine Roudet ◽  
Didier Chicot
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Steel Structures ◽  
New Method ◽  
Microplastic Deformation ◽  
Surface Phenomenon ◽  
Cyclic Loads ◽  
Cycle Fatigue ◽  
Indentation Tests

The hardness of a material shows its ability to resist to microplastic deformation caused by indentation or penetration and is closely related to the plastic slip capacity of the material. Therefore, it could be significant to study the resistance to microplastic deformations based on microhardness changes on the surface, and the associated accumulation of fatigue damage. The present work is part of a research study being carried out with the aim of proposing a new method based on microstructural changes, represented by a fatigue damage indicator, to predict fatigue life of steel structures submitted to cyclic loads, before macroscopic cracking. Here, Berkovich indentation tests were carried out in the samples previously submitted to high cycle fatigue (HCF) tests. It was observed that the major changes in the microhardness values occurred at the surface of the material below 3 μm of indentation depth, and around 20% of the fatigue life of the material, proving that microcracking is a surface phenomenon. So, the results obtained for the surface of the specimen and at the beginning of the fatigue life of the material will be considered in the proposal of a new method to estimate the fatigue life of metal structures.

A Comparison of Two Microslip Contact Models for Studying the Mechanics of Underplatform Dampers

2018 ◽  
Author(s):  
Chao Xu ◽  
Dongwu Li ◽  
Muzio M. Gola ◽  
Chiara Gastaldi
Keyword(s):  
Friction Coefficient ◽  
Friction Model ◽  
Tangential Displacement ◽  
Tangential Stiffness ◽  
Contact Loads ◽  
Contact Kinematics ◽  
Contact Models ◽  
Friction Models ◽  
Microslip Friction ◽  
Contact Parameters

In turbine blade systems, under-platform dampers are widely used to attenuate excessive resonant vibrations. Subjected to vibration excitation, the components with frictionally constrained interfaces can involve very complex contact kinematics induced by tangential and normal relative motions. To effectively calculate the dynamics of a blade-damper system, contact models which can accurately reproduce the interface normal and tangential motions are required. The large majority of works have been developed using macroslip friction models to model the friction damping at the contact interface. However, for those cases with small tangential displacement where high normal loads are applied, macroslip models are not enough to give accurate results. In this paper two recently published microslip models are compared, between them and against the simple macroslip spring-slider model. The aim is to find to which extent these models can accurately predict damper mechanics. One model is the so called GG array, where an array of macroslip elements is used. Each macroslip element of the GG array is assigned its own contact parameters and for each of them four parameters are needed: normal stiffness, tangential stiffness, normal gap and friction coefficient. The other one is a novel continuous microslip friction model. The model is based on a modification of the original classic IWAN model to couple normal and tangential contact loads. Like the GG array the model needs normal and tangential stiffness, and friction coefficient. Unlike the GG array the model is continuous and, instead of the normal gap required by the GG array, the Modified IWAN model needs a preload value. The two models are here applied to the study of the mechanics of a laboratory under-platform damper test rig. The results from the two models are compared and allow their difference, both for damper mechanics and for the complex-spring coefficients, to be assessed.

Instrumented indentation microscope applied to the elastoplastic indentation contact mechanics of coating/substrate composites

2009 ◽  
Vol 24 (6) ◽  
pp. 1950-1959 ◽  
Author(s):  
N. Hakiri ◽  
A. Matsuda ◽  
M. Sakai
Keyword(s):  
Contact Area ◽  
Film Coating ◽  
Instrumented Indentation ◽  
Thin Film Coating ◽  
Composite Systems ◽  
Indentation Tests ◽  
Film Substrate ◽  
Contact Parameters

In instrumented indentation tests for a thin film coating on a substrate (film/substrate composite), it is well known that the substrate-affected contact area estimated through conventional approximations includes significant uncertainties, leading to a crucial difficulty in determining the elastic modulus and the contact hardness. To overcome this difficulty, an instrumented indentation microscope that enables researchers to make an in situ determination of the contact area is applied to an elastoplastic film on substrates having various values of their elastic moduli. Using the indentation microscope, the substrate-affected indentation contact parameters including contact hardness of the film/substrate composites are determined directly as well as quantitatively without any undesirable assumptions and approximations associated with the contact area estimate. The effect of a stiffer substrate on the contact profile of impression is significant, switching the profile from sinking in to piling up during penetration, and resulting in the substrate-affected contact hardness being highly enhanced at deeper penetrations. Through the present experimental study, it is demonstrated how efficient that instrumented indentation microscopy is in determining the substrate-affected elastoplastic contact parameters of film/substrate composite systems.

New Deployable Structures Based on an Elastic Origami Model

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Kazuya Saito ◽  
Akira Tsukahara ◽  
Yoji Okabe
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Simple Model ◽  
Elastic Deformation ◽  
Initial Strain ◽  
New Method ◽  
The Finite Element Method ◽  
Deployable Structures ◽  
Elastic Deformations ◽  
Plate Models

Traditionally, origami-based structures are designed on the premise of “rigid folding,” However, every act of folding and unfolding is accompanied by elastic deformations in real structures. This study focuses on these elastic deformations in order to expand origami into a new method of designing morphing structures. The authors start by proposing a simple model for evaluating elastic deformation in nonrigid origami structures. Next, these methods are applied to deployable plate models. Initial strain is introduced into the elastic parts as actuators for deployment. Finally, by using the finite element method (FEM), it is confirmed that the proposed system can accomplish the complete deployment in 3 × 3 Miura-or model.

Elasto-Plastic Indentation of a Layered Medium

1974 ◽  
Vol 96 (2) ◽  
pp. 97-103 ◽  
Author(s):  
F. E. Kennedy ◽  
F. F. Ling
Keyword(s):  
Plastic Deformation ◽  
Layered Medium ◽  
Considerable Effect ◽  
Plastic Layer ◽  
The Finite Element Method ◽  
Rigid Substrate ◽  
Indentation Size ◽  
Indentation Tests ◽  
Plastic Indentation ◽  
Plastic Case

An analysis is performed, using the finite element method, of the indentation of a thin elasto-plastic layer resting on or attached to a substrate of a different material, which may also deform plastically. The indentation size, contact pressure, applied load, and amount of plastic deformation are found for the elasto-plastic case, and the results are compared with those found by an elastic analysis. It is found that plastic deformation, which occurs in all indentation tests, has a considerable effect on the results, and that the deformation in the indented layer is also affected by such variables as: the material properties of both layer and substrate, the thickness of the layer, and the condition of the interface between layer and substrate. The “piling-up” that has been observed experimentally in indentation tests is found to depend on the same variables and occurs especially when a thin layer is adhered to a more rigid substrate. The analysis is valid throughout the loading-unloading cycle.

Simulation on Driving Performance of the Vehicle Based on Modeling Tire

2011 ◽  
Vol 66-68 ◽  
pp. 373-377
Author(s):  
Yue Ying Zhu ◽  
Gui Fan Zhao ◽  
You Shan Wang ◽  
Li Liang Yin
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Simulation ◽  
Driving Performance ◽  
New Method ◽  
The Finite Element Method ◽  
Performance Simulation ◽  
Radial Tire ◽  
Simulation Results ◽  
Dynamics Models

The finite element method was used to establish model of radial tire and analysis the characteristics of tire in driving state to improve the accuracy of simulation on driving performance of off-road vehicle. The dynamics models of the vehicle and its subsystem are designed to provide an off-line dynamic simulation for vehicle driving performance. Simulation and analysis for the vehicle selected previously are made, and the simulation results are compared and analyzed in detail to prove the effectiveness of the new method.

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